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The dappled causal world for psychiatric disorders: implications for psychiatric nosology

By Rebecca Roache

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On Thursday 16th October, Professor Kenneth Kendler delivered his second (and final) Loebel Lecture, entitled ‘The dappled causal world for psychiatric disorders: implications for psychiatric nosology’. You can view it online here or listen here.

Whilst Kendler’s first lecture—summarised by Roger Crisp here—focused on empirical issues, the second lecture was more philosophical. Kendler’s key question in the second lecture could perhaps be formulated as: Given the complex aetiology of mental disorders, how can we best understand and explain how they arise?

Kendler began by providing some historical context. Using as a case study Robert Burton’s 1621 book, The Anatomy of Melancholy, Kendler observed that before the middle of the 19th century, mental disorders were not thought to have a single, clear aetiology; on the contrary, Burton provides a mind-boggling list of possible causes for melancholy. This changed in the late 19th century, when scientific advances meant that various somatic diseases could be explained in terms of elegant, simple causal mechanisms that were based on bacteriology, Mendelian models, and vitamin deficiencies. This paved the way for a reductionist quest to discover a single causal aetiology for all diseases, including psychiatric disorders. However, with the exception of the discovery that general paresis—which resulted in psychosis and other characteristically psychiatric symptoms—is caused by syphilis, attempts to discover simple aetiologies for psychiatric disorders have been unsuccessful.

What does this lack of success tell us? Kendler concedes that it might just mean that we need to keep looking.

The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.